: Respiratory illness is a leading cause of death among HIV-positive intravenous opioid users. It is critical to understand the effects of opioid use on respiratory immunity and how such effects may impact HIV disease. The proposed AREA project uses an animal model to address this issue by characterizing the effects of morphine on pulmonary immunity and influenza virus infection in rats. The project will be conducted at the University of Colorado at Denver (UCD), which is an urban university that serves many nontraditional students, trains significant numbers of graduates who pursue careers in the biomedical sciences, and is not a major recipient of NIH support. This AREA project utilizes a Rat-Adapted Influenza Virus (RAIV) model, and preliminary data show that morphine treatment impairs both resting pulmonary immunity and the innate pulmonary immune response to RAIV. Specific Aim 1 extends these findings by examining dose-effect relationships in the impact of sub-chronic and chronic morphine treatment on resting pulmonary immunity. Lymphocyte proliferation to mitogen and superantigen, natural killer cell activity, and phenotypic distribution of lymphocytes will be used to assess resting pulmonary immune status. Specific Aim 2 will assess the dose-dependency and mechanism of morphine's effects on the innate pulmonary immune response to RAIV infection. Viral replication, pulmonary inflammation, and characterization of pulmonary cell types after infection will be used to measure the response to RAIV. Specific Aim 3 will test the hypothesis that morphine treatment will cause dose-dependent reductions in RAIV-specific acquired immunity, and that activation of opioid receptors is responsible for these effects. Measurements of anti-RAIV antibodies, RAIV-specific lymphocyte proliferation, and RAIV-specific CTL activity in the lungs and peripheral blood will be used to assess acquired immunity. Future studies will utilize RAIV and bacterial infection to increase understanding of how interactions between infection, drug use, and the immune system may adversely affect HIV infection in humans. Importantly, this project will establish a new and meritorious research program that will provide increased research opportunities for UCD students.